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(Post Link) post #1 of 29 Old 27-09-16 Thread Starter
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Boost drops at 2500 rpm - remapped JTD 8V

Hi to all!

I have AR 156SW 1.9JTD 8V with 115HP stock engine which I have remapped to increase power.
I have done this 2 years ago and from time to time I changed remap to test how engine responds to different remaps.

Now, I want to resolve problem with boost around 2500 RPMs. It drops and than after this RPMs goes back up.

With full throttle around 2000 RPMs, boost rises and cars pulls wery well, for second...but than it feels that acceleration drops and after second or two (when RPMs go over 2500-2600) acceleration is again OK. Above 3000 RPMs is OK.

I have done many logs and fine tuning of N75 maps, because I suspect that maybe my vanes are too closed so boost rises too quickly at 2000 RPMs, so ECU tries to lower it with opening vanes more that is needed...so boost drops. But, as I do many corrections, I can see that if I lower N75 values, thing became worse. So I started to going up with values and I'm now reached original value of 44% at 2500 RPM, but problem still exists, however, it is less noticable than when this value is lower.

In remap I request max about 75 mm3 and 2350 mbar boost. With overboost strategy, 2400 mbar is allowed, however boost sometimes go above that. I'm not sure if ECU will try to correct that, because as I can see with normal driving, there is sometime measured boost 100 or 200 mbar higher than target boost...and ECU does nothing to correct that.

I'm wondering, why is this boost drop happening always at 2500RPMs? It looks like around 2500 RPMs turbo needs more pressure to maintain boost than on lower or upper revs.

Here I attach two logs with two different remaps, only difference is few values at last column in N75 eco and sport map, so you can see what is happaning. Logs are made on same road, in 4th gear, less than hour between runs.

Anyone have any ideas what is happening?
Attached Images
File Type: jpg 23.7-1.JPG (76.3 KB, 35 views)
File Type: jpg 23.8-1.JPG (89.4 KB, 29 views)
File Type: jpg N75_maps.jpg (181.8 KB, 42 views)
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This problem is not related to VNT.

Hint, look at injection...
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(Post Link) post #3 of 29 Old 28-09-16 Thread Starter
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Quote:
Originally Posted by TribesMan View Post
This problem is not related to VNT.

Hint, look at injection...
Hi,

yes, that was my idea also...but I can't see reason why injection will drop at this RPMs.
IQ/temp limiter, torque limiter and smoke limiter allows enough fuel. Only thing that I suspect is that maybe duration is wrong, because I modified it a little. Reason why I do that was stock duration that is not logic after 60mm3 and over 1350 bar fuel pressure. Hovewer, these values in stock maps are never used...so they are irrelevant for stock maps...but when requesting more than 60mm3 of fuel and 1350 bar pressure, I think it should be corrected.

I attached logs which includes IQ, airmass, duration, CR pressure...also some of my relevant maps. I still don't see where to search for problem.
Attached Images
File Type: jpg log_23.8-1.jpg (65.7 KB, 17 views)
File Type: jpg log_23.8-2.jpg (63.4 KB, 13 views)
File Type: jpg log_23.8-3.JPG (71.1 KB, 21 views)
File Type: jpg log_23.8-4.JPG (64.3 KB, 21 views)
File Type: jpg log_23.8-5.JPG (52.4 KB, 12 views)
File Type: jpg duration.JPG (190.0 KB, 22 views)
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Originally Posted by sike_156 View Post
Hi,

yes, that was my idea also...but I can't see reason why injection will drop at this RPMs.
IQ/temp limiter, torque limiter and smoke limiter allows enough fuel. Only thing that I suspect is that maybe duration is wrong, because I modified it a little. Reason why I do that was stock duration that is not logic after 60mm3 and over 1350 bar fuel pressure. Hovewer, these values in stock maps are never used...so they are irrelevant for stock maps...but when requesting more than 60mm3 of fuel and 1350 bar pressure, I think it should be corrected.

I attached logs which includes IQ, airmass, duration, CR pressure...also some of my relevant maps. I still don't see where to search for problem.
..and iq relevant maps
Attached Images
File Type: jpg iqtemplimit.JPG (20.7 KB, 126 views)
File Type: jpg smokelimit.JPG (90.9 KB, 16 views)
File Type: jpg torquelimit.JPG (14.2 KB, 125 views)
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Ohh, my car had same problem before it was broken. When I give load to car like heavy acceleration, or climbing. same RPM range same problem. Boost goes down, you feel it. When I look to gauge of boost, it is rising again
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(Post Link) post #6 of 29 Old 28-09-16 Thread Starter
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Originally Posted by emre2blue View Post
Ohh, my car had same problem before it was broken. When I give load to car like heavy acceleration, or climbing. same RPM range same problem. Boost goes down, you feel it. When I look to gauge of boost, it is rising again
So what was reason your car brokes? Is it related to this boost drop and did you find cause for it?

However, this afternoon I changed duration maps and try again...in logs I can still see drop of boost and IQ around 2500 RPMs, however, now clutch can't handle this torque and starts to slip around 2200-2400 RPMs.

So, even with more injection quantity via modified (increased) duration, there is still boost problem.

To be clear with duration, does anyone have correct duration map for 1.9 JTD 8V 115HP from 2005. that covers 65, 70, 75 and 80 mm3?

Stock durations in columns 65 and 70 mm3 does not look valid.
Attached Images
File Type: jpg duration_23.9.JPG (72.6 KB, 15 views)
File Type: jpg log_23.9-1.JPG (54.8 KB, 17 views)
File Type: jpg log_23.9-2.JPG (43.9 KB, 15 views)
File Type: jpg log_23.9-3.JPG (44.7 KB, 12 views)
File Type: jpg log_23.9-4.JPG (53.1 KB, 11 views)
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It was not related to the problem. But my injectors was not in good shape. I think I found why my car is broken. Organic Coolent - A Blue Liquid - Only use this don't mix with water. This f..ked my car and bleed all the water to ground while I was driving with a lot of speed. Also melted my oil cooler orings so oil and water mixed. any way I don't want to disturb the subject. but after my mods are finished we will see if this boost problem is still there.
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adjust your vnt maps properly, thats was the problem. i can see it in your logs.
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(Post Link) post #9 of 29 Old 29-09-16 Thread Starter
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Quote:
Originally Posted by mladenke View Post
adjust your vnt maps properly, thats was the problem. i can see it in your logs.
I tried that with lower values and than with higher values...but there is always same problem.

I'm totally out of idea what to try next and not sure what is going on. Is values in VNT maps for 2000-2200 RPMs to high so after that ECU drops boost, or there is noting wrong at that range, but is wrong in 2200-2600 RPM range?

I'm logging with bluetooth dongle and mobile phone (AlfaOBD), and values in logs are received one after another, there is a some time difference between them. So, if in logs is value 2500 for RPM and let say 2200 mbar boost, this boost is actually for RPMs higher than 2500. Same thing with n75 values.
Other thing, when I put pedal to the metal, sport n75 map is activated and there are lower values than in eco n75 map. I don't know how much time needs to pass (with WOT) to return to eco n75 map. When accelerating from low revs (1600-1700 RPMs) with WOT, while engine reaches 2200 RPMs ECU should already switch to eco n75 map. And in that map, at 2000-3000 RPM range there is no fluctuation of values...they are dropping with REVs.

So, please, instead of only saying that this or that map should be adjusted, can someone describe what is acctualy happening here?
I know that many different things can cause this, (lower injection time than expected, lower or higher boost than expected, IQ limiter by airflow or RPM, SOI)...but something should came first and after that all other parameters go low. Question is now...what is first parameter that goes out of expected value?

Somewhere I found that VNT maps are used only under some RPMs and after that VNT switches to closed loop mode. Is that somewhere around 2500RPMs so maybe this can cause this boost drop?
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I've been following this thread with interest in the hope than somebody might offer a bit more info than a hint or a tip to help the OP. Sadly not. I have the same issue, with a 2.4 10v, for at least 4 years now, and nobody has a solution so far. Never remapped, I've owned the car from new. Engine has been changed, valve hit a piston: related ? We don't know, new engine displayed exact same characteristics when fitted to car, but was fine in donor car. Fitted new turbo pipes, maf, filters, fuel pressure valve in pump, entire vnt controls, pipes and vacuum pump, timing checked, rechecked, cam and alt belt replaced with all tensioners and water pump, injectors checked and reconditioned, glow plugs, air box, intake piping replaced, turbo reconditioned. MAP reading correct. Rail sensor correct. Still have a flat spot/boost/fuel drop just after 2000 rpm. No codes, ecu scan shows the drop quite clearly, but all sensors/readings appear correct. EGR blanked, cat removed from exhaust. Only thing left is the fuel pump and ecu, but neither show any signs of being at fault, and pump was carried over with new engine anyway.
So if somebody knows how to begin solving this issue, can you please share it? The basic premise of this, and all other forums, is to offer assistance if one can. Without that, it begins a slow decline into uselessness.
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Quote:
Originally Posted by Hugh Myles View Post
I've been following this thread with interest in the hope than somebody might offer a bit more info than a hint or a tip to help the OP. Sadly not. I have the same issue, with a 2.4 10v, for at least 4 years now, and nobody has a solution so far. Never remapped, I've owned the car from new. Engine has been changed, valve hit a piston: related ? We don't know, new engine displayed exact same characteristics when fitted to car, but was fine in donor car. Fitted new turbo pipes, maf, filters, fuel pressure valve in pump, entire vnt controls, pipes and vacuum pump, timing checked, rechecked, cam and alt belt replaced with all tensioners and water pump, injectors checked and reconditioned, glow plugs, air box, intake piping replaced, turbo reconditioned. MAP reading correct. Rail sensor correct. Still have a flat spot/boost/fuel drop just after 2000 rpm. No codes, ecu scan shows the drop quite clearly, but all sensors/readings appear correct. EGR blanked, cat removed from exhaust. Only thing left is the fuel pump and ecu, but neither show any signs of being at fault, and pump was carried over with new engine anyway.
So if somebody knows how to begin solving this issue, can you please share it? The basic premise of this, and all other forums, is to offer assistance if one can. Without that, it begins a slow decline into uselessness.
I know it's a long shot but are you still using the original oil pump?
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No, the engine was fitted with all ancillaries that it came with. Long shot alright Paddy, whats your thinking on it ?
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No, the engine was fitted with all ancillaries that it came with. Long shot alright Paddy, whats your thinking on it ?
Years ago I had a MK2 Golf GTI with a turbo conversion. It developed a flat spot - I can't remember the exact revs but it was between 2 and 3K in every gear. Nobody could work it out until the turbo blew one day accompanied by the usual billowing smoke. I wasn't too far away from home so I thought I'd nurse it back when I discovered that the smoke disappeared at exactly the same RPM where the flat spot appeared. The conclusion was that the oil supply to the turbo wasn't sufficient at that particular number of revs hence the flat spot and eventual turbo failure. I don't know why - perhaps it was something complicated like a standing wave set up in the oil system at a particular frequency, or some sort of pressure loss throughout the whole system. Fluid dynamics isn't simple!

Told ya it was a long shot.
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Thank you for that Paddy, its a very feasible possibility. But in my case, as the flat spot was in the original engine, and still there with the replacement engine, which retained all its relevant components pertaining to this being the problem, including the turbo, it would likely be another dead end for me. I can't speak for Sike though.
It has been mentioned in this thread that we need to be looking at injection, and that sounds very much like a good place to look, but without some further guidance we may as well be looking in 10,000 haystacks for a nano needle. Perhaps that individual might oblige ?
I'd say that Golf was nice though ?
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Thank you for that Paddy, its a very feasible possibility. But in my case, as the flat spot was in the original engine, and still there with the replacement engine, which retained all its relevant components pertaining to this being the problem, including the turbo, it would likely be another dead end for me. I can't speak for Sike though.
It has been mentioned in this thread that we need to be looking at injection, and that sounds very much like a good place to look, but without some further guidance we may as well be looking in 10,000 haystacks for a nano needle. Perhaps that individual might oblige ?
I'd say that Golf was nice though ?
I've tried to increase injection duration time to cheat ECU when it "thinks" that IQ drops...so there would be enough fuel to make enough pressure for turbo...but same thing happens. I noticed that when I don't do WOT, but let say 80-90% of throttle, this is not happening. I also noticed that sometimes when accelerating (3rd gear) at half throttle and stays there on same position, car accelerates OK after I pressed gas pedal, but after second or two it feels like acceleration drops...and that I think is switching from sport maps (turbo, n75) to eco maps; also I think that I confirmed that in one of my remaps where I was rewrite x axes (IQ) in sport maps to match values in eco maps (sport maps are only up to 55 mm3, and eco up to 64 mm3 in stock).

So, I thought that this boost drop at around 2500 is also related in switching from sport to eco maps...but it does not make sense; if I do WOT at lowest RPMs, while engine reaches 2500 RPMs it takes more than 4-5 seconds...and after second or two ECU should allready switch to eco maps.

However, your problem with all stock is very strange, but as you said, your EGR is blocked, like mine...so I'm wondering if this could be problem? But, my is also switched off by EGR off switch bit in ECU.

I think that something that I don't know is happening in ECU at that RPMs; some logic in ECU software that we don't know. I'm in possession of EDC15C software documentation, but is on technical german and I don't understant it. Tried to do google translate, but I haven't found any usable info about this problem. Maybe someone knows German and is willing to try and find any related info about this problem?

Document is named Funktionsbeschreibung EDC15C B079.CC0 and is available somewhere on internet (I also found it somewhere...)
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I'd say that Golf was nice though ?
The speed of it was intoxicating, frightening even. Fat tyres and no power steering made parking a chore and there were other problems too like insufficient oil cooling. I lived abroad and the modified bits were forever breaking which sometimes meant limping over to England to get it fixed. I think if I'd known more about cars back then I could have made it so much better. Still miss it.
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Quote:
Originally Posted by sike_156 View Post
I know that many different things can cause this, (lower injection time than expected, lower or higher boost than expected, IQ limiter by airflow or RPM, SOI)...but something should came first and after that all other parameters go low. Question is now...what is first parameter that goes out of expected value?
Would it be MAF? At WOT presumably MAF is the primary control of fuel quantity, to limit smoke. Have you got a modified inlet system? Perhaps a resonance is confusing the sensor, at those revs?

Quote:
Originally Posted by Hugh Myles View Post
I've been following this thread with interest in the hope than somebody might offer a bit more info than a hint or a tip to help the OP. Sadly not. I have the same issue, with a 2.4 10v, for at least 4 years now, and nobody has a solution so far. Never remapped, I've owned the car from new. Engine has been changed, valve hit a piston: related ? We don't know, new engine displayed exact same characteristics when fitted to car, but was fine in donor car. Fitted new turbo pipes, maf, filters, fuel pressure valve in pump, entire vnt controls, pipes and vacuum pump, timing checked, rechecked, cam and alt belt replaced with all tensioners and water pump, injectors checked and reconditioned, glow plugs, air box, intake piping replaced, turbo reconditioned. MAP reading correct. Rail sensor correct. Still have a flat spot/boost/fuel drop just after 2000 rpm. No codes, ecu scan shows the drop quite clearly, but all sensors/readings appear correct. EGR blanked, cat removed from exhaust. Only thing left is the fuel pump and ecu, but neither show any signs of being at fault, and pump was carried over with new engine anyway.
So if somebody knows how to begin solving this issue, can you please share it? The basic premise of this, and all other forums, is to offer assistance if one can. Without that, it begins a slow decline into uselessness.
In sike's case the VNT demand increased during the flat spot so the ecu must (I think) have recognized the boost drop and tried to correct it. I imagine this is what would happen if something was limiting the fuel quantity.

What happens to the VNT demand in your case?
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Would it be MAF? At WOT presumably MAF is the primary control of fuel quantity, to limit smoke. Have you got a modified inlet system? Perhaps a resonance is confusing the sensor, at those revs?



In sike's case the VNT demand increased during the flat spot so the ecu must (I think) have recognized the boost drop and tried to correct it. I imagine this is what would happen if something was limiting the fuel quantity.

What happens to the VNT demand in your case?
I have measured airflow, and airflow also drops as boost drops...and than rises again. I have stock inlet system. Well, maybe it is some resonance at these revs and airflow...it would make sense, but I'm not sure that will be case on stock inlet.

Yes, VNT increases after flat spot, but actually if you see data that I provided before, VNT is lowering boost too much, to 37% at around 2300 RPM but in VNT maps for this revs should be higher than 42%. So I think that first parameter that drops is actually VNT opening, not IQ or airflow (it is also seen in logs). But why is this happening? Is it possible that ECU reduces VNT without VNT maps if overboost is detected?

Hmm....I just start to thinking something....maybe overboost strategy is doing this??
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Once you have max boost it must (surely) be controlled from the MAP sensor, not maps, to prevent overboost, so the low VNT readings at 2300rpm will be what is required to maintain max boost, not mapped values. It appears to me in your graphs that VNT increases DURING the flat spot (but it's hard to tell how the x axes line up) so the ECU is trying to get the boost back up because something - fuel limit/bearing friction etc - is reducing it.
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Originally Posted by R.T. View Post
Once you have max boost it must (surely) be controlled from the MAP sensor, not maps, to prevent overboost, so the low VNT readings at 2300rpm will be what is required to maintain max boost, not mapped values. It appears to me in your graphs that VNT increases DURING the flat spot (but it's hard to tell how the x axes line up) so the ECU is trying to get the boost back up because something - fuel limit/bearing friction etc - is reducing it.
Hmm...today I tried to do test without WOT...but little under full throttle...and here are results. It seems that problem is not related only to WOT. I tried to maintain constant throttle position (in logs it can be seen that IQ is almost constant), and as it can be seen, at 2500 RPMs boost drops, VNT goes first down than up. Same thing happens at about 50, 55 and 65 mm3...so I don't think IQ limiting is a cause. I also think that turbo is on different IQ, VNT % and boost operates on different speed at 2500 RPMs...so I don't think the issue is at turbo bearing friction. Same thing with airflow...different IQ and boost...different airflow...so intake resonance or something related is not likely. If problem shows at different RPMs than it could be related to something of that.

I'm still convinced that something in ECU software, wrong tuned maps or some logic are causing this...
Attached Images
File Type: jpg vnt_not_full_throttle.JPG (72.0 KB, 16 views)
File Type: jpg vnt_not_full_throttle2.JPG (113.5 KB, 12 views)
File Type: jpg vnt_not_full_throttle3.JPG (119.7 KB, 13 views)
File Type: jpg vnt_not_full_throttle4.JPG (115.7 KB, 11 views)
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Hmm indeed. In 2 of 4 boost and VNT appear to oscillate. You could try using the brakes to hold the revs in the flat spot for a few seconds; do the boost and power recover, or stay low, or oscillate? (Probably easiest at WOT)

PS: might still be Paddy OPlastic's exotic bearing friction theory because if I understand that correctly, it is engine speed dependent, not turbo speed.
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Hmm indeed. In 2 of 4 boost and VNT appear to oscillate. You could try using the brakes to hold the revs in the flat spot for a few seconds; do the boost and power recover, or stay low, or oscillate? (Probably easiest at WOT)

PS: might still be Paddy OPlastic's exotic bearing friction theory because if I understand that correctly, it is engine speed dependent, not turbo speed.
Good hint how to test and log!! Today when returning from job I have logged parameters while trying to maintain constant RPMs and IQ. Here are results.
Attached Images
File Type: jpg constant_rpm1.JPG (94.0 KB, 19 views)
File Type: jpg constant_rpm2.JPG (114.5 KB, 20 views)
File Type: jpg constant_rpm3.JPG (108.8 KB, 18 views)
File Type: jpg constant_rpm4.JPG (101.0 KB, 11 views)
File Type: jpg constant_rpm5.JPG (118.6 KB, 16 views)
File Type: jpg raising_rpm.JPG (86.7 KB, 16 views)
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I don't see signs of oscillation when revs are constant, so probably not sticky vanes or boost control loop instability.
The boost does slowly recover after the VNT has risen.
In graph 3 (especially) IQ remains constant(ish) even as the boost drops and the VNT rises. So as you say in post 1, the turbo seems to need more energy input during the flat spot. What would cause this?

Bearing friction.
Increased exhaust back pressure or inlet throttling.
Revs dependent connector failure on an injector.
Injection timing out. (Valve timing slightly out?)
?????

I think that's the best I can do at the moment. Anyone else want to have a go?
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I don't see signs of oscillation when revs are constant, so probably not sticky vanes or boost control loop instability.
The boost does slowly recover after the VNT has risen.
In graph 3 (especially) IQ remains constant(ish) even as the boost drops and the VNT rises. So as you say in post 1, the turbo seems to need more energy input during the flat spot. What would cause this?

Bearing friction.
Increased exhaust back pressure or inlet throttling.
Revs dependent connector failure on an injector.
Injection timing out. (Valve timing slightly out?)
?????

I think that's the best I can do at the moment. Anyone else want to have a go?
Yesterday I put another map in ECU with slightly higher N75 values around 2500 RPMs to help ECU to maintain boost level. Now that flat spot around 2500 RPM looks like less noticeable, but in logs I can still see boost drop of 0,2 bar for around two-three seconds (wot in 5th gear from low RPMs) so maybe is that just my subjective feeling.

However, searching on internet I found this:

Alfa Romeo forum: slight drop in boost.. 2.4 jtd

Look for JTD Lovers post. He states that this boost drop is normal and that is programmed in ECU for emissions. It would be nice to find that info in EDC15C technical description...if anyone knows german.
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Hopefully my latest logs are attached here. 1500-4000 rpm in forth, into 5th, 1500-3200 rpm for both.
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File Type: xls 2.xls (14.0 KB, 15 views)
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